Aggression is a complex behavior expressed in many different social contexts. Often abused, yet essential for the survival of organisms, little is known of the biological roots of this behavior. While model systems may not duplicate aggression in all of its many human manifestations, they can be highly informative about: the relative importance of genes, hormones and experience in laying down patterns of aggression in nervous systems; detailing the neural circuitry involved; and addressing questions of how animals choose among the varied complex behaviors available within their behavioral repertoires. It is the last two matters that are the major focus of the present application. In recent years, the Kravitz laboratory has established a fruit fly model of aggression making this important behavior available for experimental analysis in an organism that is highly suitable for genetic analysis. With fruit flies aggression is complex and is shown by both males and females, the animals engage in many other inter-related behaviors, and the behaviors can be quantitatively analyzed. In addition, however, the genome has been sequenced and incredibly powerful methods are available that allow experimental manipulations to be performed with fruit flies that cannot yet even be approximated in most other animal model systems. Recently, it has been found that the same gene that determines who flies court also determines whether flies fight like males or females. The present application extends these studies and has the following Specific Aims: I. To explore decision-making between courtship and aggression, two sexually dimorphic patterns of behavior in flies, by mapping and manipulating the fruitless/doublesex-associated circuitry within the subesophageal ganglion (SOG), the taste center in fruit fly brains; II. To map the distribution of receptors for amines and peptides associated with the SOG circuitry; and III. To introduce genes into neurons that can alter the function of these nerve cells in behaving animals and to begin to address the question of how the same neurons differ in male and female animals. These studies use a wide variety of state-of-the-art genetic, behavioral and anatomical methods in exploring these Aims. For example, in collaborative studies with the Chiang laboratory in Taiwan, neuronal maps will be made that will allow examination in great detail of the possible connections between individual neurons involved in courtship and aggression. The focus will be to define the brain circuitry important in aggression and courtship at much higher levels of resolution than are now available, and then to ask how that circuitry gets established in fly brains and how animals choose between behavioral responses when conflict situations arise. PUBLIC HEALTH RELEVANCE: All organisms, including humans, must be capable of rapidly evaluating social situations and selecting proper responses from what may be a wide variety of possible behavioral choices. Such selections must be made correctly in order to allow the survival of organisms both as individuals and as species. How organisms make such choices and how patterns of innate behavior of great complexity get established in nervous systems are not well understood, and are the theme of this application.